The Beekeeper’s Companion Since 1861

The Classroom

The Classroom – October 2023

- October 1, 2023 - Jamie Ellis - (excerpt)

The Classroom - ABJ - Jamie Ellis
Q  Filtering cartridges

I have a question about the filtering cartridges used with masks during the application of formic acid and the vaporization treatment with oxalic acid. When should they be changed? At what point does their effectiveness no longer provide the necessary protection?

Marie-Hélène Majeau
Québec, August


These are very important questions. All products administered to honey bee colonies for the purpose of controlling pests/diseases have labels that specify how the products are to be used. These labels include information on the personal protective equipment (PPE) that must be worn while administering the product. PPE is intended to protect the applicators from any known harmful effects of the product. Common PPE includes chemical-resistant gloves, goggles, long pants, shoes, and even respirators.

Respirators are used when the compound is known to cause harmful impacts as a result of volatilization. Not all respirators are created equal. They come in different styles, shapes, sizes, etc. The exact respirator you need to use will be specified on the product label. Some of these respirators use cartridges to filter out the chemical to which you do not want to be exposed. There are different cartridges used for different compounds. The one you need will be specified on the product label.

The University of Florida, where I work, has a Pesticide Information Office. Faculty in that office produce training materials and answer questions related to safe pesticide use. Appropriate to your questions, they published a document entitled “Respirators for Pesticide Applicators.” You can find the article here: In that document, the author (Dr. Fred Fishel, retired faculty member) stated the following:

Chemical cartridges should be replaced according to the manufacturer’s recommendations or the pesticide label or when the wearer notices odor or experiences irritation. Prefilters will extend the life of chemical cartridges in dusty conditions. Mechanical filters should be replaced when breathing becomes difficult, the filter is damaged, or as specified by the manufacturer or the pesticide label. If no instructions are provided, replace cartridges and filters when the workday is over.

I hope this information is helpful. Please have a look at the referenced document for even more information about this topic

Fungus on bees

 The president of my local bee club said to contact [you] and ask if this fungus I found would be a threat to our local honey bees (Figure 1). I found it about 2 miles (~3.2 km) from my apiary in Mcdowell County, North Carolina at Mt. Ida wilderness in Marion. After some research, I believe it is a European hornet infected with Beauveria bassiana fungus. This appears to have happened naturally considering the area I found it in but some people use this fungus as a natural mycological insecticide under the name BioCeres. Do we need to do something to protect local honey bees from this? What are your thoughts?

Savannah Tedesco
North Carolina, August


Interesting picture. Thanks for sharing. I believe that the insect in the picture is some sort of bee rather than a hornet. It is hard for me to tell with certainty, as the fungus has grown around some of the key diagnostic areas of the individual. Nevertheless, I believe it to be a bee, perhaps even the giant resin bee (though that is just a guess —

So, what about that fungus? It is impossible to know what this species of fungus is just by looking at it. It would take an expert on fungi and molecular tools to determine the exact species. It is also impossible to know if the fungus was responsible for the death of the bee or if it just grew on an already-dead bee, which remains an equal probability in this case. My guess, just from context clues, is that there is no reason to believe this fungus is a threat to honey bees.

I do want to spend a minute addressing your comment about Beauveria bassiana. This is a soil-dwelling fungus and it occurs naturally in many locations globally. This fungus is known to infect many types of insects. It can lead to the death of infected insects. For this reason, it is well studied and used as an entomopathogenic fungus, just as you note. This simply means that it is marketed and sold for the control of various arthropod species. It is certainly possible that it was the cause of death for the insect in the picture you provided. However, it is just impossible to know without having the actual insect sample. Even if it was responsible for the bee’s death, it does not really pose a widespread threat to honey bees. It is already present in the environment, without leading to any documented cases of honey bee colony losses (though, it can kill honey bees that encounter it at high enough doses).



I have kept bees for 25+ years and so have seen most textbook behaviors first hand. Recently, however, I witnessed something really strange that has me scratching my head. I was monitoring some nucs with new unmated queens, checking queen development and for the beginning of laying activity. However in this small hive, after much searching, I could not find the queen. I then noticed her court, in a perfect circle around her — and she was face down inside a cell! No amount of “tickling” by my index finger could coax her out. After quite a while, she slowly backed out and started parading across the comb as expected. At the time, she had not started laying. Have you seen this behavior before and do you have any idea what she was up to?

Steve Davis
Idaho, August


I have seen this behavior in the past. There are at least three things that could be happening. First, the queen could be inspecting the cell to see if it is clean and to determine what size it is. She does this in advance of laying an egg in the cell. This process usually only lasts a few seconds, but it can take longer. Second, new queens feed themselves. I am not sure if you had a close look at the inside of the cell once the queen withdrew, but it is possible that she was head first in a nectar/honey cell feeding. Finally, she could be resting. This is a common resting position for queens. I am sure there are other possible reasons for this as well, but these are usually the default thoughts I have when I observe this type of behavior. In this context, I think the queen was simply taking a break from the burden of laying 2,000 eggs per day.


Q  Odd Queen Behavior

 We most often see pictures of large, disgusting masses of small hive beetle (SHB) larvae after they have overtaken a weak hive, and are eating (and sliming) their way to the hive entrance. Once at the entrance, larvae drop to the ground where they crawl away from the hive and burrow into the ground where they pupate into mature beetles. At least this is my understanding. Do small numbers of SHB eggs hatch, with only a few (unseen by the beekeeper) larvae making it to the entrance without being stopped by the bees? Is the SHB life cycle continual even in healthy hives?

Kirk Kirksey
Texas, August


Small hive beetles do reproduce cryptically, even when you do not see it happening. (Incidentally, the same is true for wax moths.) If you see adult SHBs in your hives, you can rest assured that they are reproducing. There was a nice study by Spiewok and Neumann (2006) who showed this to be the case. You can read their manuscript here:

Honey bees are pretty good at stopping mass SHB reproduction like that you describe in your question. They do this by harassing the SHBs that hide in cracks/crevices around the nest. The bees will station guards at these locations, ultimately confining the beetles in prison. Occasionally, the SHBs will escape confinement and make it to the brood nest or where the bees store pollen. There, the female SHBs will lay eggs in cracks/crevices that bees often are unable to access. My colleagues and I have shown in the past that female SHBs will bite small holes in the cappings and side walls of brood cells, insert their ovipositor (egg laying appendage) and lay eggs on/around the developing honey bee. SHB larvae will emerge from the eggs, feed on the brood and/or pollen, exit the hive one evening, and burrow into the soil where they pupate.

Colleagues and I also showed that bees can even detect these low levels of cryptic reproduction and remove the SHB eggs/young larvae from the nest. However, they undoubtedly miss some eggs/larvae just due to the cryptic nature of SHB reproduction when colonies are otherwise healthy. You can put trays under a healthy hive, one in which you see no obvious SHB damage, and collect SHB larvae in the debris that falls. It is likely this cryptic reproduction that keeps SHB populations steady in an apiary. Fortunately, bees keep this behavior in check more often than not, minimizing the occurrence of these mass reproduction events.


Q  Small hive beetles

 Your recent article on the use of B402 in the August edition of ABJ is very clear and helpful, thank you. I am wondering about treating wooden frames with no new foundation after I have removed and disposed of infested foundation. I have been told that wax moth eggs are hidden in the wood, but do not know if this is accurate. For winter, I store frames in plastic bins with lids. Frames stored in bins as well as many stored in stacked deeps in my honey house were riddled with moth larvae. This is my first experience with this pest, and I appreciate any advice you
can give.

Dee Johnson


I am sorry that you are meeting wax moths for the first time. They are certainly pesky critters! Wax moth caterpillars consume the adulterants associated with beeswax. These adulterants include the cast skins of the developing bees, pollen debris, etc. That is why the caterpillars have a clear affinity for dark/black combs located in the colony’s brood nest rather than the newer, less-adulterated combs bees use to store honey in the supers.

Once the caterpillars have finished feeding, they spin a cocoon around themselves and begin to pupate. They can do this in the comb that they consume, but they often do it in/on the woodenware in the nest. This can include affixing their cocoons to the frames, hive walls, bottom board, lid, etc. When attaching their cocoons to the woodenware, they often excavate little boat-shaped indentions in the wood. Over time, and given enough caterpillars doing this, this can affect the structural integrity of the wood, especially the frames.

The good news is that wax moths do not eat wood, they only affix their cocoons to it. Thus, the best way to protect the woodenware is to remove the moths’ food, making them not want to be around the woodenware in the first place. It sounds like you already have done this, given you removed the infested foundation. Any wax moth eggs left in/on the wood may hatch, but the caterpillars will have nothing to eat (i.e., no wax). Correspondingly, the moths are highly unlikely to damage the wood. There is no need to treat the wood otherwise.

My team and I produced a document on …